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AUTOMATIC VISITOR COUNTER PROJECT REPORT

INTRODUCTION

AUTOMATIC VISITOR COUNTER

A counter that can change its state in either
direction, under control of an up–down selector input, is known as an up–down
counter. The circuit given here
can count numbers from 0 to 9999 in up and down
modes depending upon the state of the selector. It can be used to count the
number of persons entering ascript type="text/javascript">
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hall in the up mode at entrance gate. In the down
mode, it can count the number of persons leaving the hall by decrementing the
count at exit gate. It can also be used at gates of parking areas and other
public placesIn this circuit, two infrared (IR) sensor modules
are used each for up and down counting, respectively. Whenever an interruption
is observed by the first IR sensor, it increments the counter value. Similarly,
when the second sensor detects an obstacle, the count is decremented.

The count value is calculated depending upon
the sensors’ input and is displayed on a set of four seven segment displays by
using the concept of multiplexing (for concept of multiplexing refer seven
segment multiplexing). The data pins of each 7-segment display are connected to
port P2 of the microcontroller P89V51RD2 The first four pins of port P1
(P1^0-P1^3) are connected to control pins to enable a particular 7-segment.
P1^5 & P1^6 are configured as input pins at which the sensors are
connected. The sensor inputs are defined as up and down selector modes for the
counter in the code. Each time the first sensor is blocked, it gives a high
signal at P1^5 and the count value gets incremented. The value gets decremented
when P1^6, connected to second sensor, gives high input. At each step, the
value of the counter is sent to be displayed on the segments.

COMMON ANODE AND
COMMON CATHODE

In a CA display, the anodes for the seven segments
and the decimal point are joined into a single circuit node. To illuminate a
segment in a CA display, the voltage on a cathode must be at a suitably lower
voltage (about .7V) than the anode. In a CC display, the cathodes are joined
together, and the segments are illuminated by briging the anode voltage higher
than the cathode node (again, by about .7V). The Digi lab board uses CA
displays. The seven LEDs in each digit are labelled a-g. Since the Digilab
board uses CA displays, the anodes for each of the four digits are connected in
a common node, so that four separate anode circuit nodes exist (one per digit).
Similar cathode leads from each digit have also been tied together to form
seven common circuit nodes, so that one node exists for each segment type.
These four anode and seven cathode circuit nodes are available at the J2
connector pins labelled A1-A4 and CA-CG. With this scheme, any segment of any
digit can be driven individually. For example, to illuminate segments b and c
in the second digit, the b and c cathode nodes would be brought to a suitable
low voltage (by connecting the corresponding circuit node available at the J2
connector to ground), and anode 2 would be brought to a suitable high voltage
(by connecting the corresponding circuit node available at the J2 connector to
Vdd).